Purpose: Transcranial focused ultrasound (FUS) delivers highly focused acoustic energy to a small region of the brain in a noninvasive manner. Recent studies have revealed that PUS, which is administered either in pulsed or continuous waves, can elicit or suppress neural tissue excitability. This neuromodulatory property of PUS has been demonstrated via direct motion detection, electrophysiological recordings, functional magnetic resonance imaging (fMRI), confocal imaging, and microdialysis sampling of neurotransmitters. This study presents new evidence of local increase in glucose metabolism induced by PUS to the rat brain using FDG (18-fludeoxyglucose) positron emission tomography (PET).
Methods: Sprague Dawley rats underwent sonication to a unilateral hemispheric area of the brain prior to PET scan. The pulsed sonication (350 kHz, tone burst duration of 0.5 ms, pulse repetition frequency of 1 kHz, and duration of 300 ms) was applied in 2 s intervals for 40 mm immediately after the FDG injection via tail vein. Subsequently, the PET was acquired in dynamic list-mode to image FDG activity for an hour, and reconstructed into a single volume representing standardized uptake value (SUV). The raw SUV as well as its asymmetry index (AI) were measured from five different volume-of-interests (VOIs) of the brain for both hemispheres, and compared between sonicated and unsonicated groups.
Results: Statistically significant hemispheric changes in SUV were observed only at the center of sonication focus within the FUS group [paired t-test; t(7) = 3.57, p